In a mortar and pestle, pound julienned Thai basil into a fine paste. Add grachai and pound into a paste. Add the shrimp paste and green curry paste and pound to mix.
In a heavy-bottomed pot, bring about ¾ cup of the coconut milk to a full boil over medium heat. Add the curry paste and sauté, stirring frequently, until coconut oil starts to separate from the paste, 3-5 minutes.
Add chicken thigh and stir to mix with the paste.
Add the chicken stock, remaining 1 cup of coconut milk, palm sugar and 1 Tablespoon of the fish sauce. Grab the makrut lime leaves and twist them to bruise and release aroma, then tear them into chunks and add them to the pot.
Bring to a simmer and let simmer gently for 10-15 minutes or until the chicken is fork tender.
Meanwhile, if using Thai eggplant, cut them into bite-sized pieces.
Once the chicken is done simmering, add the Thai eggplant and keep pushing them into the curry for the first minute.
Turn off the heat and add the red peppers and stir to mix, then add the Thai basil and stir to mix. Taste and adjust seasoning with more of the fish sauce as needed. Serve with jasmine rice.
